1. Field of the Invention
The present invention relates to a correlation detection apparatus for detecting a correlation between received data and code for synchronous capture/tracking in a CDMA communication system or the like, and a Fourier transform apparatus appropriate to the correlation detection apparatus.
2. Description of the Related Art
For synchronous capture/tracking of communication between a base station and a mobile station in a W-CDMA communication system, inverse-spread processing (correlation detection processing) for obtaining correlation between a spread received signal and code is required, and for this processing a matched filter is employed.
In a case where a preamble (RACH preamble) of a random access channel (RACH) is detected by using a matched filter, as the number of taps is large due to delay of signal transmission between the base station and the mobile station, the circuit scale of the matched filter is also very large.
Accordingly, it is difficult to perform the detection of the RACH preamble only by hardware processing.
On the other hand, the RACH preamble may be detected by software inverse-spread processing using a DSP.
In the software inverse-spread processing, development costs of the base station and mobile station can be reduced and high-level functions can be attained.
However, as a very large amount of operations is required for detection of RACH preamble by using the DSP, conventionally the software inverse-spread processing has not been realized without difficulty.